Term 2

Question 1

Define aniseikonia

Answer 1

Aniseikonia is the terminology whereby there is a difference in the perceptual size and shape of images between both eyes

Question 2

What are the 6 layers of an MAR coated lens

Answer 2

You’ve got hydrophobic layer that is water repellent, hard coat for anti scratch, anti reflective coating for the reduction of glare from artificial sources of light.. x2

Question 3

Anisometropia

Answer 3

A difference in refractive error, between the two eyes, either one hypermetropic and other myopic, or on the contrary a large difference between the two refractive errors.

Question 4

Asthenopia

Answer 4

Reduction in light transmission which MAR coatings avoid..

Question 5

Name features of MAR coating

Answer 5

Hydrophobic, anti static, buffer, anti reflective, scratch resistant
Allows 99% of light through
Cosmesis element

Question 6

Driving lens examples

Answer 6

Duravision by Zeiss
Drive X lens by Seiko
Reduces the oncoming glare from vehicles, increasing visual clarity and perception

Question 7

RISKS OF UV EXPOSURE

Answer 7

Skin cancer, cataracts, retinal damage

Question 8

Relationship between tints and UV

Answer 8

Not all tints contain UV blockers, yet they should contain UV coating
UV coating can be applied to certain lenses with no level of tints, however there is a correlation

Question 9

What is a graduated tint

Answer 9

Graduated tints are generally darker at the top and lighter towards the bottom, offering a cosmesis sense of style

Question 10

Describe photochromic lenses

Answer 10

These lenses react to UV light and through any exposure, darkens depending on temperature and light intensity - as modern cars have a UV windscreen filter, they not useful when driving turning dark

Question 11

What direction of light do polarised lenses eliminate

Answer 11

They eliminate horizontal glared light - unpolarised light vibrates in many different directions potentially causing some discomfort, however polarised light travels and vibrates in one particular direction

Question 12

Infrared radiation

Answer 12

Arise from industrial processes like furnaces and industries where heat is employed;
CR39 not useful material for IR absorbing filter ideally glass
IR filters often colour green due to ferrous oxide - pilots

Question 13

Benefits of yellow, orange tints

Answer 13

Areas of low light contrast settings and blue light emissions

Eg - football, soccer, snow sports

Question 14

Benefits of amber, rose tints

Answer 14

Enhancing colours and not suitable for driving conditions

Question 15

Dark amber and brown tints

Answer 15

Melanin - decreasing blue light emissions, improving visual clarity and enhancing contrast

E.g - fishing, golf, cycling

Question 16

Grey tints

Answer 16

doesn’t alter the perception of colours, natural perception and minimises brightness and glare

Any outdoor activity, reduces eye strain

Question 17

Green tints

Answer 17

Soothing cool tones, enhances contrast, whilst preventing eye strain in bright conditions

Good, tennis baseball

Question 18

Why bifocal recommendations

Answer 18

Clear vision for two distances
Wide and stable view
More convenient than two separate

Question 19

Disadvantages

Answer 19

Less cosmesis
No intermediate
Limited view with small seg

Question 20

What base prism does round seg innervate

Answer 20

Base down prism hence better to go for plus distance prescription

Question 21

What base direction do D and C segs innervate

Answer 21

Base up prism hence suited to minus rx

Question 22

Advantage of C over D seg

Answer 22

Offer bette cosmetics

Question 23

Feature of executive Seg

Answer 23

Leat cosmesis as line running though lens
No jump henc offers best optics

Question 24

Where should heights be taken from

Answer 24

Lower limbus

Question 25

Define best form lens

Answer 25

Aimed to reduce or eliminate certain aberrations to allow clear vision focussing on retina, opposing distortions

Question 26

What factors do longitudinal and transverse aberrations arise from

Answer 26

Dispersive properties of optical materials
Higher refractive index = lower v value hence higher dispersive

Question 27

Pincushion distortion

Answer 27

Occurs in positive lenses whereby as you move away from optical centre the lens magnifies and extends

Question 28

Advantages of aspheric lenses

Answer 28

Control of distortion
Less spec mag
Thinner and lighter lens hence better cosmesis
Considerably flatter
Off axis performance